Rehabilitation interventions in the patient with obesity

This book has a unique focus on physiotherapy techniques and training methods that are ideally suited for the obese patient. Despite its related comorbidities and disability, not to mention its pandemic proportions, the impact of obesity on individual capacities and rehabilitative outcomes is often neglected by physiotherapists and physical trainers alike. The number of disabled subjects who are also obese is now increasing worldwide, as is the rate of obese patients admitted to post-acute rehabilitation units. The effective rehabilitative treatment of these patients involves special multidisciplinary considerations.

This book fills that gap, by gathering evidence-based chapters addressing not only the physiological limitations of obese subjects but also state-of-the-art, novel and specific treatment and training modalities suited for these patients. Though the content is primarily intended for rehabilitation practitioners (physiotherapists, nutritionists, dieticians, psychologists, PRM specialists), it will also benefit students and researchers engaged in this particular multidisciplinary field. The book’s ultimate goal is to increase professionals’ awareness of this multidisciplinary area, and to provide a pragmatic guidebook for those who want to engage in the rehabilitation of patients who are also obese.

• Language: English
• Publisher: Springer
• Release date: Mar 30, 2020
• ISBN: 9783030322748

Book preview

© Springer Nature Switzerland AG 2020

P. Capodaglio (ed.)Rehabilitation interventions in the patient with obesityhttps://doi.org/10.1007/978-3-030-32274-8_1

1. Physical Activity and Endurance Training Modalities: Evidences and Perspectives

Davide Malatesta¹  , Paolo Fanari², Alberto Salvadori² and Stefano Lanzi³

(1)

Institute of Sport Sciences of the University of Lausanne (ISSUL), University of Lausanne, Lausanne, Switzerland

(2)

Pulmonary Rehabilitation Department, San Giuseppe Hospital, Istituto Auxologico Italiano Piancavallo, Verbania, Italy

(3)

Division of Angiology, Heart and Vessel Department, Lausanne University Hospital (CHUV), Lausanne, Switzerland

Davide Malatesta

Email: [e-mail]

Keywords

Aerobic fitnessWeight managementHIITModerate-intensity exerciseFatmax trainingHypoxiaNoninvasive ventilation

Key Points

Daily physical activity and endurance training are crucially important for improving aerobic and metabolic fitness and health levels in individuals with obesity.

Continuous moderate- and high-intensity exercise training are two complementary, rather than exclusive, training tools.

Innovative training modalities as normobaric hypoxic training and noninvasive ventilation may be promising and useful training methodologies.

Promotion of daily physical activity in any forms and accumulated in a minimum of 10-min bouts during the day should be encouraged rather than focusing solely on structured endurance exercise training.

Obesity has been recognized as one of the most important growing problems in our society, and its prevention and treatment are a public health priority [1]. Obesity is a manifestation of positive energy balance over an extended period of time: the daily energy intake is higher than the daily energy expenditure. This is due to an increase in food energy supply, essentially due to an increase and simple food access [2], associated with an increase in sedentary activities and a decrease in physical activities, related to a reduction in movement at work, an increase in domestic mechanization of daily tasks, and an increase in passive transportation [3]. A global prevalence of insufficient physical activity of 27.5% has recently been reported in the world’s population [3]. Although, based on this evidence, it seems intuitive that the rise of obesity prevalence in the world is attributable to decreased energy expenditure due to insufficient physical activity level. This relationship is not often confirmed and supported by scientific evidence in the literature. In fact, the energy balance is a complex and dynamic process and the physical activity influences different factors, which interact with each other and modify the energy balance independently of the energy expenditure spent during the physical activity [4]. Moreover, some recent meta-analyses reported that the impact of physical activity on weight loss is marginal with 0–2 kg of weight loss for aerobic/endurance exercise and it can be increased to 10 kg when the endurance training is combined with low-caloric restriction (1000–1500 kcal/day) [5–8] (Table 1.1). Therefore, as reported in the new physical activity recommendations of American College of Sports Medicine [5], to increase the effect of the physical activity on weight loss it seems important to increase the duration (volume) of physical activities performed at moderate-to-vigorous intensity from 150 min, for improving or maintaining health, to 300–400 min per week for promoting clinically significant weight loss [5, 7] (Table 1.2). However, independently of weight loss, the pivotal role of physical activity in the prevention and treatment of obesity is its well-known effect on the improvement of cardiorespiratory (aerobic) and metabolic fitness and health, decreasing the chronic disease and mortality risks associated with obesity [9, 10].

Table 1.1

Weight loss and clinically significant weight loss for the different training modalities (modified from Swift et al. [7])

Table 1.2

Recommendations for weekly physical activity duration according to the American College of Sports Medicine (ACSM [5]; Swift et al. [7])

1.1 Definition and Classification of Physical Activity

Physical activity is defined as any bodily movement produced by skeletal muscles that results in energy expenditure [11]. Physical activity can be classified across four domains, which can be grouped in two main categories. First is the daily physical activity: (1) physical activity to work, (2) physical activity in the household, and (3) physical activity for transport. Second is the physical activity during leisure time (i.e., sports and active recreation) also defined as exercise in the scientific literature and related to all structured and supervised training programs by physical trainers or clinical exercise physiologists or specialists in adapted physical activities. These two types of physical activity should be considered and used in weight management programs aiming to prevent and treat obesity.

1.2 Daily Physical Activity

Some authors have recently reported that the duration of the moderate-to-vigorous physical activity (MVPA) should exceed 10 min per bout to accumulate more time spent in bouted MVPA in order to reduce the risk of incident obesity [12]. For each 10-min increase in bouted MVPA, the risk of obesity is reduced by 21%. On the contrary, this decreased obesity risk was not associated in accumulated time spent per day in bouted MVPA of less than 10-min duration [12]. These recent findings support the pivotal role of the accumulation and repetition of minimum 10-min MVPA bouts during the day. However, the posture time allocation of daily physical activity is different in obese than in lean sedentary individuals [13]. The former spends less time standing/ambulating (−152 min) and more time sitting (+164 min) than their lean counterparts. This induced a lower daily total energy expenditure (−350 kcal/day) in obese compared with lean individuals. Moreover, this different posture time allocation did not change when obese individuals lost weight or when lean individuals gained weight [13] highlighting the difficulty to change the daily physical activity behavior in obese or sedentary people. For this reason, it is important to develop strategies to increase the energy expenditure associated with daily physical activity without changing its posture time allocation. The use of commercially available unstable shoes, increasing the energy expenditure of standing and walking by 5–7% when compared with conventional shoes [14], may be a valuable solution to increase the non-exercise activity thermogenesis (NEAT, [15]). This could be complementary to the promotion of daily physical activity in any forms and accumulated in a minimum of 10-min bouts during the day that should be encouraged using and promoting options for the environments in which individuals may elect to engage in physical activity.

1.3 Endurance Training Modalities

Several studies have investigated different exercise training programs with different modalities, frequencies, intensities (moderate or high), and durations to evaluate the optimal dose-response relationship between endurance exercise training and health-related outcomes in overweight/obese individuals.

1.3.1 Moderate-Intensity Exercise Training

Continuous moderate exercise training (CMT) normally corresponds to 46–63% of the maximal oxygen uptake ( $$ \dot{V}{\mathrm{O}}_{2\max } $$ ) (or 64–76% of the maximal heart rate (HRmax)) (Table 1.3) [16]. CMT was initially adopted in sedentary and overweight/obese individuals because it is safe, feasible, and well tolerated. Moreover, because this training modality increases the reliance on fat oxidation rates during exercise, it was logically prescribed to this population.

Table 1.3

Description of different exercise training modalities for practical implications

CMT continuous moderate exercise training, Fat max training exercise training intensity elicits maximal fat oxidation, HIIT high-intensity interval training, SIT sprint interval training, HR max maximal heart rate, HRR HR reserve, $$ \dot{V}{\mathrm{O}}_{2\max } $$ maximal oxygen uptake, $$ \dot{V}{\mathrm{O}}_2R $$ oxygen uptake reserve, RPE ratings of perceived exertion (6–20 RPE scale), ↓ decrease, ↑ increase or improvement

The level of adaptations is expressed as a function of the number of + symbols

Exercise intensities are adapted from Garber et al. [16]

Although previous observations reported successful weight and fat mass loss following CMT (without energy restriction) in sedentary overweight and obese men and women [17], others investigations found no significant changes across different CMT durations (i.e., 50%, 100%, 150% of public health recommendation) [18]. These findings suggest that exercise training is not necessarily accompanied by changes in body weight and/or fat mass in this population. This may be explained by compensatory mechanisms (physiological and behavioral) occurring during an exercise program [19]. Recently, Flack et al. [20] showed that similar energy compensation occurred following two moderate exercise training programs with distinct energy expenditures (1500 vs. 3000 kcal/week). Interestingly, percentage and kg of body fat decreased significantly only in the 3000 kcal/week group. These results suggest that compensatory responses are not proportional to exercise energy expenditure and that greater exercise volume may therefore overcome compensatory behavior limiting exercise-induced negative energy balance [20].

Concerning the effect of this type of training on aerobic and metabolic fitness and health in individuals with obesity, it has been shown that 8-week CMT at 65–70% $$ \dot{V}{\mathrm{O}}_{2\max } $$ may be effective to increase fat oxidation, which may, at least in part, provide a mechanism for the enhanced insulin sensitivity in obese individuals [21]. Indeed, the authors showed that the oxidative capacity increased after intervention, leading to an increased rate of mitochondrial fat oxidation [21]. This phenomenon was associated with a significant reduction of lipid intermediates, which was inversely correlated with glucose tolerance [21]. Finally, an increased $$ \dot{V}{\mathrm{O}}_{2\max } $$ has also been found after intervention. Consistent with these results, other studies [22, 23] have also shown that 16-week CMT at 60–70% HRmax may increase $$ \dot{V}{\mathrm{O}}_{2\max } $$ and insulin sensitivity in overweight/obese individuals and that the best predictor of improved insulin sensitivity is the increase in fat oxidation [22]. In contrast, it has also been indicated that the impact of muscle oxidative capacity and lipid oxidation on the regulation of insulin sensitivity remains controversial [24], suggesting that other mechanisms (such as the excessive plasma non-esterified fatty acid (NEFA) levels [25, 26] or flux [27]) are likely involved.

1.3.2 Individualized Moderate-Intensity Exercise Training (Fatmax Training)

As the balance of substrates might be altered during exercise in metabolic diseases, it seems judicious to individualize the exercise training to consider the individual metabolic profile [28]. During submaximal incremental exercise, whole-body fat oxidation rates (calculated applying the classical stoichiometric equations of indirect calorimetry [29]) increase from low to moderate and decrease from moderate to high exercise intensities [28, 30–32], implying that exercise intensity (Fatmax) elicits maximal fat oxidation (MFO) [33]. Thus, a moderate exercise training program targeted at individualized Fatmax appears to be a good candidate [28, 34, 35]. In obese individuals, the training intensity that elicits MFO normally corresponds to ~45–50% $$ \dot{V}{\mathrm{O}}_{2\max } $$ (60–65% HRmax) [36–39] (Table 1.3).

Bordenave et al. [40] showed no significant decrease in body mass (BM), body mass index (BMI), fasting plasma glucose, and insulin concentrations after a 10-week program of individualized Fatmax training in diabetic patients. However, these authors found a significant increase in Fatmax and MFO and a greater reliance to fat oxidation during exercise after intervention, which was related to an increase in muscle oxidative capacity [40]. The effects of individualized Fatmax training were also tested in overweight/obese adults. Consistent with previous studies, this training modality increases Fatmax, MFO, and the reliance on fat oxidation during exercise [41, 42] concomitant with changes in insulin sensitivity after 8 weeks of training [41]. However, resting plasma glucose and insulin concentrations, as well as lipid profile variables (total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL)), were unchanged after intervention [41, 42]. In addition, it also has been recently shown that a shorter 4-week program of individualized Fatmax training may increase fat oxidation rates during exercise and insulin sensitivity in overweight/obese men [39].

1.3.3 High-Intensity Exercise Training

It is now well known that many people do not meet the minimum physical activity recommendations [3]. It seems that lack of time is one of the most commonly barriers to fail to achieve this goal. Therefore, it is of importance to develop more time-efficient training programs with regard to improving exercise training adherence. A good candidate to achieve this goal might be high-intensity interval training (HIIT). Indeed, although it has been suggested that this training modality may not be feasible and is associated with a low level of adherence in overweight/obese individuals [43], it has now been well established that HIIT rapidly induces adaptations that are linked to improved health-related outcomes in sedentary and overweight/obese individuals [44–46]. Moreover, this training intensity is perceived to be more enjoyable than CMT in obese individuals [47]. High-intensity exercise normally corresponds to 64–90% $$ \dot{V}{\mathrm{O}}_{2\max } $$ (or 77–95% HRmax) [16] (Table 1.3). HIIT is composed of brief bursts of vigorous intensity interspersed with periods of rest or low-intensity exercise [45].

Because there are many factors (intensity, duration, and number of intervals and duration and nature of the recovery) that may describe this form of training, a HIIT classification based on the literature is needed. The HIIT mainly used in obese individuals, the aerobic HIIT, may be divided into two categories. First is short aerobic HIIT [48–50], which consists of 8–12 repetitions of 60 s at 85–95% HRmax interspersed with 60 s of recovery or low intensity. Second is long aerobic HIIT [51–54], which consists of four repetitions of 4 min at ~90% HRmax followed by 3 min of recovery. Additionally, another HIIT model intervention is the Wingate-based HIIT (or sprint interval training (SIT)), which consists of 4–6 repetitions of 30 s of all out cycling effort against a supramaximal workload interspersed with 4–5 min of rest [45]. However, although SIT (8–30 s of all out) has been performed in individuals with metabolic diseases [47, 55–60], this type of HIIT may be unsuitable for some individuals. This highlights the importance of alternative HIIT strategies to adopt this training in clinical settings [45, 46, 48, 49, 52, 53, 61].

It was previously demonstrated that only 2 [60] or 4 [58] weeks of SIT (3 days/week; protocol involved ~35 min/session with only 2–3 min of exercise) was a sufficient stimulus to increase $$ \dot{V}{\mathrm{O}}_{2\max } $$ in overweight/obese men [60] and in obese women [58]. However, less evidence has been found with regard to the effect of SIT on increased insulin sensitivity in obese individuals [62]. Whyte et al. [60] demonstrated an increase in insulin sensitivity after 24 h, but not after 72 h, after a 2-week SIT. Similarly, resting fat oxidation also increased only after 24 h but not after 72 h [60]. In addition, there were no differences in plasma NEFA concentrations or other lipid profile variables (e.g., TC, TG, HDL) after the intervention [60]. Recent investigations also showed no significant changes in insulin sensitivity after longer SIT training program (i.e., 12 weeks) [55]. In contrast, short aerobic HIIT (10 × 60 s at ~90% HRmax interspersed with 60 s of recovery for 3 days/week for 2 week) has been shown to simultaneously increase the oxidative capacity of muscle and insulin sensitivity in sedentary overweight/obese individuals [48] and improve 24-h blood glucose control in overweight/obese diabetic subjects [49]. Finally, it has previously been shown that a single exercise bout consisting of 4 min performed at 90% HRmax may increase $$ \dot{V}{\mathrm{O}}_{2\max } $$ and reduce blood pressure and fasting glucose to a similar extent as 4 × 4 min performed at 90% HRmax for 10 weeks (3 times/week) in overweight individuals [63].

1.3.4 Comparison Between Moderate- and High-Intensity Exercise Training

Although both moderate- and high-intensity exercise training have been shown to improve health-related outcomes, to determine which training intensity is associated with additional risk reduction and well-being in clinical population, it is now imperative to compare these two training modalities. Despite the large amount of experimental studies, inconclusive and inconsistent results exist on the superiority, or not, of HIIT compared to CMT in individuals with obesity. It is important to note that energy expenditure has not always been matched among training groups, leading to difficulty interpreting the results.

Previous studies have initially compared the effects of different intensities at which CMT was performed in individuals with obesity. Van Aggel-Leijssen et al. [64] have shown that low-to-moderate exercise training (40% $$ \dot{V}{\mathrm{O}}_{2\max } $$ for 57 min) for 12 weeks increases total fat oxidation during moderate-intensity exercise compared to moderate-to-high exercise training at 70% $$ \dot{V}{\mathrm{O}}_{2\max } $$ (33 min duration, matched for energy expenditure) in overweight/obese individuals. This result was due to an increase in intramuscular triglyceride oxidation after intervention, which indicated that low-to-moderate exercise training might be an effective strategy to improve fat oxidation during exercise in this population. However, $$ \dot{V}{\mathrm{O}}_{2\max } $$ was significantly increased in both groups after intervention (+11% and +15%, respectively). In addition, Salvadori et al. [65, 66] have recently shown that CMT (30 min at ventilatory threshold, ~70% HRmax) for 4 weeks increases insulin sensitivity, decreases β-cell function, and decreases plasma NEFA concentrations at rest and during exercise compared to a mixed exercise training program composed of 25 min at ventilatory threshold (~70% HRmax) followed by 5 min at 85% HRmax (intensity higher than ventilatory threshold) in severely obese individuals. However, this mixed exercise program promoted a higher fat mass loss associated with an increase in post-training plasma NEFA concentrations at rest and during exercise when compared to CMT alone. This phenomenon, probably driven by an increased flow of some lipolytic substances as growth hormone (GH), catecholamines, and others, may be linked to an excessive mobilization of NEFA from body fat without an equally concomitant NEFA utilization [65]. Although these two short training programs were not matched for energy expenditure (i.e., higher energy expenditure during mixed exercise training program) and both did not lead to significant changes in $$ \dot{V}{\mathrm{O}}_{2\max } $$ after intervention, these findings may suggest that mixed exercise program with the final 5-min bout above the ventilatory threshold may be recommended to induce a larger fat mass loss in the initial training period [65, 66].

More recently, several studies have compared the effects of CMT versus HIIT on the aerobic and metabolic fitness and health in obese individuals. In a recent meta-analysis which includes experimental studies ≥4-week intervention, it has been shown that the improvements in aerobic fitness are similar after CMT or HIIT in obese individuals [67]. Interestingly, in a subgroup analysis, which differentiates the interval bout duration (i.e., ≥2 min or <2 min), the results showed that only HIIT performed with bouts of ≥2-min duration had greater effectiveness than CMT on improving aerobic fitness [67], highlighting the importance of the interval duration during HIIT with regard to increase in the cardiorespiratory fitness in this population. This is in line with recent observations showing that only 4 × 4 min performed at 90% HRmax for 6 weeks significantly improved $$ \dot{V}{O}_{2\max } $$ compared to 10 × 60 s at $$ \dot{V}{\mathrm{O}}_{2\max } $$ load or CMT in overweight/obese adults [68]. In addition, it is also interesting to note that greater improvements in aerobic fitness after HIIT were found when the energy expenditure was similar to that of CMT [67].

Concerning glucose metabolism, this meta-analysis showed that there was no significant difference in improving fasting glucose and insulin levels, but also highlighted that the majority of the included individuals were adults without metabolic diseases [67]. Indeed, Tjonna et al. [52], when comparing CMT and long aerobic HIIT (16-week duration), showed that insulin sensitivity increased more after a long aerobic HIIT compared to a CMT intervention in individuals with metabolic syndrome. Moreover, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) levels increased only after long aerobic HIIT, suggesting a potential increase in mitochondrial biogenesis only after HIIT program.

Results from this meta-analysis also showed that both HIIT and CMT induce significant reduction in TC, but that only HIIT reduces LDL relative to CMT, highlighting the importance of HIIT in CV risk reduction and prevention of CV diseases [67]. Finally, it has also recently been shown that both CMT and HIIT are effective, in a similar extent, in body fat and waist circumference reductions (associated with no changes in body weight) in obese individuals [69].

It is interesting to note that recent studies also investigated the effect of very short HIIT and CMT training durations (i.e., ≤2 week) in obese individuals. Skleryk et al. [57] showed no significant metabolic or skeletal muscle adaptations after only 2 weeks of reduced-volume SIT (8–12 × 10-s all out sprints) or CMT (30 min at 65% $$ \dot{V}{O}_{2\max } $$ ) in obese men. Indeed, no significant changes in $$ \dot{V}{O}_{2\max } $$ , plasma NEFA, insulin, glucose and insulin resistance, or protein expression of glucose transporter 4 (GLUT-4) were found after intervention. In contrast, Lanzi et al. [70] recently showed that 2 weeks of an individualized moderate-intensity continuous training (40–50 min at Fatmax) or short aerobic HIIT (10 × 60-s intervals at ~90% HRmax interspersed with 60-s recovery) were both effective for the improvement of aerobic fitness and fat oxidation rates during exercise in obese men with II and III class of obesity. Although there was no significant difference in increased $$ \dot{V}{\mathbf{O}}_{\mathbf{2}\max } $$ , HIIT had tendency toward promoting a more marked increase in $$ \dot{V}{\mathbf{O}}_{\mathbf{2}\max } $$ compared to Fatmax training (+8% and 4%, respectively). On the other hand, fasting insulin and insulin resistance were reduced only after moderate-intensity training at Fatmax, suggesting the importance of exercise duration for improving insulin sensitivity in obese individuals [71].

Based on the above reported considerations, different endurance training modalities seem to be effective to improving health-related outcomes in overweight/obese individuals. With regard to the necessity of increasing exercise training adherence in a real-world setting [72], we suggest that continuous moderate- and high-intensity exercise training are two complementary, rather than exclusive, training tools which should be performed for improving aerobic and metabolic fitness and other health-related outcomes.

1.4 Innovative Training Modalities

1.4.1 Normobaric Intermittent Hypoxic Exercise Training

As already presented above, physical exercise training is an important lifestyle behavior for weight management, fitness, and health benefits. However, adherence to prescribed or spontaneous exercise remains low [73] and often declines over time in obese individuals inducing to a plateau in weight loss or partial or total recovery of lost weight 6 months after the beginning of intervention [74, 75]. Furthermore, obesity may increase joint stresses during walking, which likely modify gait pattern [76–81], and may contribute to lead eventually musculoskeletal pathologies (e.g., lower-extremity osteoarthritis, rheumatoid arthritis, and/or low back pain) [82]. This may increase the dropout during exercise training programs [83] and, thus, limit their beneficial effects in weight management interventions in obese individuals [84]. For this reason, it is imperative that alternative and innovative strategies are developed for individuals with obesity to increase variation, adherence, and effectiveness of exercise training programs to finally match current exercise recommendations [5].

Among these innovative strategies, normobaric hypoxic training is used and compared with equivalent normoxic training, to improve weight loss and cardiometabolic markers in individuals with obesity (see for review [74, 75, 85–87]). Normobaric hypoxia (i.e., simulated altitude (2500–3000 m) via a reduced inspired O2 fraction (14–15 FiO2) usually obtained using hypoxic chamber) is defined as a reduced O2 supply to tissues caused by decreases in O2 saturation of arterial blood with normal barometric pressure. Normobaric hypoxic training, which activates the hypoxia-inducible factor (HIF), may play a pivotal role in effective metabolism regulation (weight maintenance, glucose homeostasis, O2 transport and satiety) and, thus, could be a useful tool to treat obesity. Recent systematic review and meta-analysis [74] supports this concept showing that, similar to normoxic training, normobaric hypoxic training results in significant decreases in body weight, fat mass, weight-to-hip ratio, waist circumference, and in several cardiometabolic markers (triglycerides, LDL, HDL, systolic and diastolic blood pressure). However, only the magnitude of reductions in triglycerides and higher muscle mass gain was greater in hypoxic than in normoxic training. Moreover, these mostly similar results between the two interventions may be obtained using lower exercise intensity in normobaric hypoxic than in normoxic training [88–90]. Fernandez Menendez et al. [91] recently reported that a 3-week normobaric hypoxic (3000 m) walking training program at slower preferred walking speed than in normoxia elicited similar responses in terms of body mass and composition, energetics and mechanics of walking, and metabolic risk markers in individuals with obesity. However, this slower walking speed in hypoxia may reduce joint loads and stresses and increase adherence to training compared to normoxic training performed at faster walking speed and, thus, with higher risk of orthopedic injury [90, 92] and dropout during intervention. According to recent practical applications and recommendations for normobaric hypoxic training [74], this training should start using low-to-moderate intensity and include the following features: 4–6 weeks of 2–3 sessions of 60–90 min at 55–65% of $$ \dot{V}{\mathrm{O}}_{2\max } $$ or 60–70% of maximum heart rate at 13–14% of FiO2. Then, HIIT in moderate level of hypoxia (FiO2, 14–17.2%) should be added always in combination with other sessions of endurance training. HIIT sessions should include a duration of 30–60 min/session, using intervals of 8–30 s all-out followed by 3 min of active recovery at 55–65% of peak power output performed 3–4 times/week. This second part of HIIT hypoxic training could induce an additional effect in reducing fat and body mass and maximizing muscle growth [93–95]. It has also been suggested that, to optimize the effect of normobaric hypoxic training, saturation levels of 75–89% should be targeted and used to increase the hypoxic stress and stimulus [91].

1.4.2 Noninvasive Ventilation (NIV) and Proportional Assist Ventilation (PAV) During Physical Training

Noninvasive ventilation (NIV) is able to improve work capacity in individuals with obstructive pulmonary diseases as well as in patients with restrictive thoracic disorders [96, 97]. Obese individuals must overcome some peculiarities which alter respiratory mechanics like a reduced lung compliance, an increased chest wall resistance, antagonistic activity of respiratory muscles, and modified work on the abdominal viscera. They suffer from dyspnea even during mild exertion, partly by an increased oxygen cost of breathing [98].

Interesting results have been obtained in obese individuals with obstructive sleep apnea (OSA) already treated with continuous positive air pressure (CPAP) when adding NIV during physical training or respiratory muscle training (RMT – isocapnic hyperpnea). This latter is able to improve walking distance by increasing respiratory muscle endurance [99]. Aerobic fitness, assessed by $$ \dot{V}{\mathrm{O}}_{2\mathrm{peak}} $$ , significantly improved after 3 months of the combination of exercise plus RMT and exercise plus NIV when compared with exercise alone. Moreover, the use of NIV during exercise training produces a dramatic reduction in systolic as well in diastolic blood pressures versus exercise alone, with a likely protective effect on cardiovascular function, and a more important reduction of waist circumference at the end of the training period [100].

Another type of NIV is the proportional assist ventilation (PAV), which represents an extension of the activity of the patient’s own respiratory muscles. PAV generates inspiratory pressures in proportion to inspired flow and inspired volume such that the ratio between airway pressure and instantaneous patient-generated pressure is approximately 1. This method gives some advantages like reduction of peak airway pressure required to sustain ventilation, less risk of overventilation, and preservation of homeostatic control mechanisms and patient’s own reflex. On the whole, PAV is able to unload the resistive and elastic burdens of the ventilatory system [101]. During a cyclo-ergometer exercise, PAV has shown to increase the exercise endurance in more than 50% obese individuals [102]. Interestingly, in agreement with findings in patients affected by restrictive thoracic disorders, obese responder individuals have lung volumes that are lower than those of nonresponders [102].

1.5 Conclusions

Daily physical activity and endurance training are crucially important for improving aerobic and metabolic fitness and health levels. Their role in weight loss is marginal and this may become clinically significant only whether a higher exercise duration (300–400 min/session) is used and/or exercise is combined with caloric restriction. In structured endurance training, the moderate-intensity continuous and high-intensity interval trainings seem to be both effective to improving health-related outcomes and increasing adherence and variation during training interventions and should be considered two complementary training tools in overweight/obese individuals. Moreover, innovative training modalities as normobaric hypoxic training and noninvasive ventilation may be promising and useful for improving fitness and health. However, one approach that may be effective is to encourage the accumulation of moderate-to-vigorous physical activity throughout the day by increasing steps of ambulatory movement rather than focusing solely on structured periods of more traditional forms of exercise [103].

Acknowledgment

The authors thank Elsevier for the permission to reuse Figures and Tables of the manuscript of Swift et al. [7].

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